Nucleophilic displacement method for synthesis of non-rigid PBZ polymers

ABSTRACT

Azole rings, such as oxazole and thiazole rings, can activate an aromatic ring bonded to a leaving group such as a halogen atom so that the aromatic ring will undergo aromatic nucleophilic substitution. The reaction is useful for making ethers, thioethers and amines containing azole rings. In particular, monomers having azole rings, activated aromatic rings with leaving groups and nucleophilic moieties can react under conditions of aromatic nucleophilic displacement to form non-rigid rod PBZ polymers. The non-rigid rod PBZ polymers can be used to form molecular composites with rigid rod PBZ polymers which molecular composites are not substantially phase separated.

BACKGROUND OF THE INVENTION

The invention relates to the synthesis of polybenzoxazole (PBO),polybenzimidazole (PB) or polybenzothiazole (PBT) and related polymers(hereinafter referred to as PBZ polymers).

PBZ polymers are a known class of polymers which contain a plurality ofmer units comprising at

(1) a first aromatic group (Ar¹); and

(2) a first azole ring which is fused with the first aromatic group.

Each mer unit preferably further comprises

(3) a second azole ring which is fused with the first aromatic group,and

(4) a divalent group (DL), which is inert with respect to all reagentsfor making PBZ polymers under polymerization conditions. bonded by asingle bond to the 2-carbon of the second azole ring

Those mer units ordinarily comply with one of the two formulae ##STR1##wherein: Ar¹ is a first aromatic group as previously described;

DL is a divalent group as previously described: and

each Z is independently chosen from the group consisting of --O--, --S--or --NR--, wherein R is an aliphatic or aromatic group which does notinterfere with polymerization.

PBZ polymers, their chemical structure, their properties and theirsynthesis are described in depth in numerous references such as 11 Ency.Poly. Sci & Eng., Polybenzothiazoles and Polybenzoxazoles, 601 (J. Wiley& Sons 1988: Wolfe et al., Liquid Crystalline Polymer Compositions andProcess and Products, U.S. Pat. No. 4,703,103 (Oct. 27, 1987); Tsai etal., Method for Making Heterocyclic Block Copolymer, U.S. Pat. No.4,578,432 (Mar. 2, 1986); Wolfe et al., Liquid CrystallinePoly(2,6-Benzothiazole) Compositions, Process and Products, U.S. Pat.No. 4,533,724 (Aug. 6, 1985); Wolfe, Liquid Crystalline PolymerCompositions, Process and Products, U.S. Pat. No. 4,533,693 (Aug. 6,1985) and Wolfe et al., Liquid Crystalline Polymer Compositions andProcess and Products, U.S. Pat. No. 4,533,692 (Aug. 6, 1985), which areincorporated herein by reference.

It is known in the art to synthesize PBZ polymers by the reaction of afirst monomer comprising:

(1) a first aromatic group (Ar¹);

(2) a first o-amino-basic moiety bonded to said first aromatic group,which o-amino-basic moiety contains:

(a) a primary amine group bonded to the first aromatic group: and

(b) a hydroxy, thio or amine group bonded to the first aromatic group inortho position with respect to the primary amine group;

(3) an azole-forming group bonded to the first aromatic group which iseither a second o-amino-basic group or an "electron-deficient carbongroup",

and a second monomer comprising:

(1) a divalent group which is inert with respect to all reagents underreaction conditions;

(2) an "electron-deficient carbon group", such as a carboxylic acid oracid salt; and

(3) an azole-forming group which may be a second "electron-deficientcarbon group" or, if the divalent group comprises an aromatic group, ano-amino-basic group.

The known syntheses for PBZ polymers ordinarily conform to one of thefollowing two formulae: ##STR2## wherein: each Ar¹ is a first aromaticgroup:

each Z is an oxygen atom, a sulfur atom or --NR--, wherein g is analiphatic or aromatic group which does not interfere with polymerizationand each Z is bonded to the first aromatic group (Ar¹) ortho to aprimary amine group (in the monomer) or the nitrogen atom of the azolering in which it is located (in the polymer);

DL is a divalent group as previously described: and

each Q is an electron-deficient carbon group as previously described.

Those polymerizations have a number of drawbacks. First, polymerizationis ordinarily carried out in a strong mineral acid such aspolyphosphoric acid or a mixture of methanesulfonic acid and phosphoruspentoxide. Such acids are difficult to work with and must be washed fromthe resulting polymer by time-consuming rinsing over periods as long as24 hours or longer. Second, monomers containing the o-amino-basic groupare oxidatively unstable and must be stored as hydrogen halide salts,which are converted back to the basic monomer in the polymerizationvessel by a time-consuming dehydrohalogenation step. Third, in the knownsyntheses the concentration of solids in the reaction mixture cannotordinarily exceed 10 to 15 percent, so that large reaction vessels arenecessary to synthesize small amounts of polymer.

What are needed are alternative processes for synthesizing PBZ polymerswhich do not rely upon the reaction of an o-amino-basic group with anelectron-deficient carbon group to link monomers and which can avoidsome or all of the drawbacks of the prior art processes.

SUMMARY OF THE INVENTION

The first aspect of the present invention is a process for synthesizinga di-aromatic ether, thioether or amine wherein one aromatic group isbonded to an azole ring, said process comprising the step of contacting:

(1) an azole-containing compound having:

(a) an azole ring:

(b) an aromatic group bonded to the 2-carbon of said azole ring: and

(c) a leaving group bonded to said aromatic group in a position suchthat it is activated by said azole ring,

and

(2) a displacing compound having:

(a) an organic moiety which is not electron-withdrawing and which isinert with respect to all reagents under reaction conditions;

(b) a nucleophilic moiety linked to said organic moiety, whichnucleophilic moiety is a nitrogen atom having a hydrogen atom or inertorganic substituent or an oxygen atom or a sulfur atom; and

(c) a counter-moiety bonded to said nucleophilic moiety which can easilybe removed therefrom,

under conditions such that the counter-moiety is removed from thenucleophilic moiety and an ether, thioether or amine linkage is formedbetween the aromatic group of the azole-containing compound and theorganic moiety of the displacing compound. The process of the presentinvention is useful to make compounds having two aromatic groups, one ofwhich is bonded to an azole ring, linked by an ether, thioether or aminegroup. Such compounds are useful as lubricants. antioxidants and opticalbrighteners.

A second aspect of the present invention is a process for synthesizingnon-rigid-rod PBZ polymer comprising polymerizing, under conditionssuitable for nucleophilic substitution reactions, one or moredifunctional monomers, each said monomer independently containing:

(1) an organic moiety which is inert with respect to all reagents underreaction conditions: and

(2) two reactive groups selected, such that a polymer is formed, fromthe class consisting of:

(a) azole-containing groups having: an azole ring bonded to said organicmoiety, an aromatic group bonded to the g-carbon of said azole ring, anda leaving group bonded to said aromatic ring in a position where it isactivated by said azole ring: and

(b) displacing groups having: a nucleophilic moiety, which is an oxygenatom, a sulfur atom or a nitrogen atom, bonded to said organic moiety:and a counter-moiety bonded to said nucleophilic moiety,

whereby a non-rigid-rod PBZ polymer is formed.

A third aspect of the present invention is a compound comprising:

(1) a first aromatic group;

(2) an azole ring fused to said first aromatic group;

(3) a second aromatic group bonded to the 2-carbon of said azole ring;

(4) a leaving group bonded to said second aromatic group in a positionwhere it is activated by said azole ring;

(5) a nucleophilic moiety, as previously defined, linked to said firstaromatic group in a position not ortho to the 4- or 5-carbon of theazole ring; and

(6) a counter-moiety, as previously defined, bonded to said nucleophilicmoiety.

These compounds are useful AB-monomers in a process to synthesize PBZpolymers.

A fourth aspect of the present invention is a compound comprising;

(1) an unfused first aromatic group (Ar¹), which comprises two aromaticmoieties (Ar^(1a) and Ar^(1b)) linked by a bond or a divalent linkingmoiety (D) which is inert with respect to nucleophilic aromaticsubstitution;

(2) a first azole ring fused with one aromatic moiety (Ar^(1a)) of saidunfused first aromatic group, and a second azole ring fused with theother aromatic moiety (Ar^(1b)) of said unfused first aromatic group;

(3) a second aromatic group (Ar²) bonded to the 2-carbon of said firstazole ring and a third aromatic group (Ar³) bonded to the 2-carbon ofsaid second azole ring; and

(4) a first leaving group bonded to said second aromatic group and asecond leaving group bonded to said third aromatic group.

Those compounds are useful AA-monomers in a process to synthesize PBZpolymers.

A fifth aspect of the present invention is a Z polymer synthesized bythe polymerization process previously described. PBZ polymers of thepresent invention can be formed into useful objects by known processes.PBZ polymers of the present invention show thermal stability superior tothat of related PBZ polymers synthesized by conventional processes.

A sixth aspect of the present invention is a thermoplastic PBZ polymercomprising a plurality of repeating unit which contain;

(1) a first aromatic group;

(2) an azole ring fused to said first aromatic group;

(3) a second aromatic group bonded to the 2-carbon of said azole ring;and

(4) an oxygen, sulfur or nitrogen atom linked to said first aromaticgroup and bonded by a single bond to a second aromatic group of anadjacent unit.

Polymers of the present invention are thermoplastic and can be molded toform useful objects according to known methods.

A seventh aspect of the present invention is a molecular compositecomprising a first polymer which is a rigid rod PBZ polymer and a secondpolymer having a plurality of repeating units which contain;

(1) a first aromatic group;

(2) an azole ring fused to said first aromatic group;

(3) a second aromatic group bonded to the 2-carbon of said azole ring;and

(4) an oxygen, sulfur or nitrogen atom linked to said first aromaticgroup and bonded by a single bond to a second aromatic group of anadjacent unit.

Molecular composites of the present invention can be shaped to formuseful shaped articles, such as fibers and films, according to knownmethods.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The following terms, which are used repeatedly throughout thisapplication, have the meanings and preferred embodiments set outhereinafter unless further limited in the Specification.

o-Amino-basic moiety--a moiety bonded to an aromatic group, whicho-amino-basic moiety contain

(1) a first primary amine group bonded to the aromatic group and

(2) a hydroxy, thiol or secondary amine group bonded to the aromaticgroup ortho to said primary amine group.

It preferably comprises a hydroxy or thiol moiety, and most preferablycomprises a hydroxy moiety. If the o-amino-basic moiety contains asecondary amine group, the organic substituent on the amine nitrogen maycomprise an aromatic or an aliphatic group but preferably comprises analkyl group. The organic substituent preferably comprises no more thanabout 6 carbon atoms, more preferably no more than about 4 carbon atomsand most preferably no more than about 1 carbon atom.

Aromatic group (Ar)--any aromatic ring, fused ring system or unfusedring system. Each aromatic group may independently be heterocyclic butis preferably carbocyclic and more preferably hydrocarbyl. Eachheterocyclic aromatic group is preferably a nitrogen-containingheterocycle.

Each aromatic group may be bonded to substituents which are stable inmineral acid, such as halogens, phenylsulfone moieties, alkoxy moieties,aryloxy moieties or alkyl groups. Each aromatic group is preferablybonded to no substituents other than those specified hereinafter.Organic substituents on aromatic groups preferably comprise no more thanabout 6 carbon atoms.

Size is not critical as long as the aromatic group is not so big that itprevents further reactions of the moiety in which it is incorporated.Fused aromatic groups preferably comprise no more than about 10 carbonatoms, not including any organic substituent on the aromatic group.

Unfused aromatic groups comprise two aromatic moieties joined by bond ora divalent linking moiety (D) which is inert with respect to allreagents under reaction conditions. Each aromatic moiety preferablycomprises no more than about 10 carbon atoms and more preferably no morethan about g carbon atoms. The divalent linking moiety preferablycomprises no more than about 12 carbon atoms and more preferably no morethan about 8 carbon atoms. The divalent linking moiety may comprise, forinstance, a sulfonyl group; a carbonyl group; an oxygen atom; a sulfuratom; or an alkyl group, a halogenated alkyl group or a third aromaticmoiety linked to the other two by sulfonyl groups, carbonyl groups oroxygen atoms. Moieties within the divalent linking moiety are preferablychosen from the group consisting of sulfonyl groups, carbonyl groups,oxygen atoms and aromatic groups. Examples of unfused aromatic groupsinclude a biphenyl group, a diphenylketone group, a diphenylsulfonegroup, a diphenyl ether group, a diphenoxybenzene group, adibenzoylbenzene group, a diphenyl alkylene group, or adibenzoylalkylene group.

Except as specifically directed hereinafter, each aromatic group ispreferably a single ring comprising no more than about six carbon atoms,and more preferably is a mono-, di-, tri- or tetra-functional benzenering.

Azole ring--an oxazole, thiazole or imidazole ring. The carbon atombonded to both the nitrogen atom and the oxygen, sulfur or secondnitrogen atom is the g-carbon, as depicted in formula 3 ##STR3## whereinZ is --O--, --S-- or --NR--; and R is an aromatic or an aliphatic groupand preferably an alkyl group. R preferably comprises no more than about6 carbon atoms, more preferably no more than about 4 and most preferablyno more than about 1. Each azole ring is independently preferablyoxazole or thiazole and more preferably oxazole. In PBZ polymers, the 4-and 5-carbon atoms are ordinarily fused with an aromatic group.

Azole-forming moiety--an "o-amino-basic moiety" or "electron-deficientcarbon group", as those terms are defined herein.

Counter-moiety (Y)--any group which can dissociate from the nucleophilicmoiety (oxygen, nitrogen or sulfur atom) to which it is bonded, eitherby action of the solvent or by a catalyst, under reaction conditions.Examples of counter-moieties include alkali metal ions or R₃ Si-- orH--, wherein each R is independently a hydrocarbyl or substitutedhydrocarbyl moiety. Each R is preferably an alkyl group, more preferablyan alkyl group comprising 1 to g carbon atoms and most preferably amethyl group. Counter-moieties are preferably sodium, potassium orlithium ions or hydrogen atoms or trialkylsilyl moieties, and are morepreferably sodium, potassium or lithium ions or trimethylsilyl moieties.

Electron-deficient carbon group (Q)--any group containing a carbon atomwhich can react in the mineral acid with an o-amino-basic moiety to forman azole ring, such as the groups listed in column 24, lines 59-66 ofU.S. Pat. No. 4,533,693, which is incorporated herein by reference andsuch as a trihalomethyl group or an alkali metal carboxylate group.Preferred electron-deficient carbon groups are carboxylic acids or acidhalides. Halogens in electron-deficient carbon groups are preferablychlorine, bromine or fluorine and are more preferably chlorine.

Leaving group (L)--any group capable of being displaced by the anion ofa nucleophilic moiety bonded to an aromatic group under reactionconditions. Leaving groups may be, for instance, a halogen atom, analkoxy group, an aryloxy group or a nitro group. The leaving group ispreferably a halogen atom or a phenoxy group. It is more preferably achlorine or a fluorine atom and is most preferably a fluorine atom.

PBZ polymer--A polymer from the group of polybenzoxazoles andpolybenzobisoxazoles (PBO), polybenzothiazoles and polybenzobisthiazoles(PBT) and polybenzimidazoles or polybenzobisimidazoles (PBI). For thepurposes of this application, the term "polybenzoxazole (PBO)" refersbroadly to polymers in which each unit contains an oxazole ring bondedto an aromatic group, which need not necessarily be a benzene ring. Theterm "polybenzoxazole (PBO)" also refers broadly topoly(phenylene-benzobisoxazole)s and other polymers wherein each unitcomprises a plurality of oxazole rings fused to an aromatic group. Thesame understandings shall apply to the terms polybenzothiazole (PBT) andpolybenzimidazole (PBI). As used in this application, the term alsoencompasses mixtures. copolymers and block copolymers of two or more PBZpolymers, such as mixtures of PBO, PBT and/or PBI and block or randomcopolymers of PBO, PBI and PBT.

Rigid Rod PBZ polymer--An "intrinsic" or "articulated" rigid rod PBZpolymer as the terms "intrinsic" and "articulated" are defined in Hwang,"Processing, Structure and Properties of Liquid Crystalline PBTPolymer", Kansai Committee of the Society of Fiber Science andTechnology. Japan, Post Symposium on Formation, Structure and Propertiesof High Modulus and High Tenacity Fibers 23-26 (Aug. 26, 1985); Evers etal., "Articulated All-Para Polymers with 2,6-Benzobisoxazole,2,6-Benzobisthiazole, and 2,6-Benzobisimidazole Units in the Backbone",14 Macromolecules 925 (1985); Evers, "Thermooxidatively StableArticulated Benzobisoxazole and Benzobisthiazole Polymers", 24 J. Poly.Sci. Part A 1863 (1986) and Evers et al., Articulated Para-OrderedAromatic Heterocyclic Polymers Containing Diphenoxybenzene Structures,U.S. Pat. No. 4,229,566 (Oct. 21, 1980).

Intrinsic rigid rod polymers are essentially rectilinear and have apersistence length comparable to their contour length. Articulated rigidrod polymers comprise a plurality of essentially rectilinear moietiesjoined by a relatively small number of non-linear moieties. Rigid rodPBZ polymers used in the present invention are preferably intrinsicrigid rod polymers. If articulated, they preferably comprise on averageno more than about 1 non-linear mer unit for each 9 essentiallyrectilinear mer units.

Nucleophilic Substitution Process

Nucleophilic substitutions for halogens and other leaving groups onactivated aromatic rings are known reactions. The activating groupbonded to the aromatic ring in those known reactions is ordinarily asulfonyl group, a carbonyl group, a sulfoxide group, a nitro group, anitrile group or an azo group. See, e.g., Robinson et al., Capacitorwith a Polyarylenepolyether Dielectric, U.S. Pat. 3,264,536 (Aug. 2,1986); Blinne et al., Aromatic Polyether-Sulfones, U.S. Pat. 4,065,437(Dec. 27, 1977); Barr et al., Production of Polyarylene Ether Sulphonesand Ketones, U.S. Pat. No. 4,232,142 (Nov. 4, 1980); Bier et al.,Process for the Production of Aromatic Ethers and Aromatic Polyethers,U.S. Pat. 4,474,932 (Oct. 2, 1984); Rimsa et al., Circuit BoardSubstrates Prepared from Poly(aryl ether)s, U.S. Pat. No. 4,550,140(Oct. 29, 1985); Daniels, U.S. Pat. No. 4,771,945 (Dec. 8, 1987); andWoo et al., Process for Forming Arylether PolymersU.S. Pat. No.4,794,155 (Dec. 27, 1988), which are incorporated herein by reference.

It has surprisingly been discovered that an azole ring bonded at the2-carbon to an aromatic group will activate a leaving group bonded tothe aromatic ring sufficiently for that leaving group to be displaced ina nucleophilic substitution.

Therefore, nucleophilic substitution reactions can be practiced upon anazole-containing compound comprising;

(1) an azole ring;

(2) an aromatic group bonded to the 2-carbon of said azole ring; and

(3) a leaving group bonded to said aromatic group in a position suchthat it is activated by said azole ring.

Azole rings and the 2-carbon of an azole ring are previously defined.Likewise, suitable and preferred leaving groups are also previouslydefined.

The leaving group must be bonded to the aromatic group in a positionwhere it is activated by the azole ring. The leaving group and the azolering are preferably bonded to the same six-membered ring or fused ringsystem. The leaving group and the azole ring are more preferably bondedto the same six-membered ring. Most preferably the aromatic group is asix-membered ring. The leaving group is highly preferably bonded to thearomatic group in ortho or para position with respect to the azole ring,and is most preferably in para position with respect to the azole ring.Of course, the aromatic group should not have substituents whichinterfere, sterically or otherwise, with the displacement of the leavinggroup. Preferably, no organic substituent having a formula weight inexcess of 16 is ortho to the leaving group. More preferably nosubstituent is ortho to the leaving group. Most preferably, the aromaticgroup has no substituents other than those specifically named.

The azole-containing compound can be synthesized by obvious variationsof processes familiar to persons of ordinary skill in the art. Forinstance, they can be synthesized by substitution of reagents intoprocesses described in Eckenstein et al., 3 Helv. Chim. Acta. 1353(1950); Hoffman, Imidazole and its Derivatives, 6 The Chemistry ofHeterocyclic Compounds 33-50; Wiley, The Chemistry of Oxazoles, 37 Chem.Rev. 401 (1945); Van Es et al., Substitution of Some,4,5-Diphenyl-Oxazoles and -Imidazoles, and Some Related Compounds, 1963J. Chem. Soc 1363 (1963); and Schrage, Method of Preparing 2-ArylBenzoxazoles and 2-Aryl Benzothiazoles, U.S. Pat. No. 4,107,169 (Aug.15, 1978), which are incorporated herein by reference

The azole-containing compound is contacted with a displacing compoundcontaining an organic moiety, a nucleophilic moiety bonded to theorganic moiety and a counter-moiety bonded to the nucleophilic moiety.The organic moiety can be any moiety which is not electron withdrawingand which inert with respect to all reagents under reaction conditions.The organic moiety preferably comprises an alkyl group or an aromaticgroup and more preferably comprises an aromatic group. It preferablycomprises no more than about 12 carbon atoms, more preferably no morethan about 6 carbon atoms. When the organic moiety is aromatic, it hasthe descriptions and preferred embodiments previously used to describearomatic groups. The previous discussion regarding substituents ortho tothe leaving group also applies to substituents ortho to the nucleophilicmoiety.

The nucleophilic moiety is an oxygen atom, a sulfur atom or a nitrogenatom having a substituent. It is preferably an oxygen atom or a sulfuratom. If it is a nitrogen atom, then it must also be bonded to ahydrogen atom or an organic substituent which is inert with respect toall reagents under reaction conditions. The nitrogen atom is preferablybonded to a phenyl ring, an alkyl group having no more than about gcarbon atoms, or a hydrogen atom, and is more preferably bonded to ahydrogen atom. The counter-moiety of the displacing compound conforms tothe definition and preferred embodiments previously defined.

Many displacing compounds are well-known and commercially available. Thedisplacing compound can be, for instance, an alcohol having from one tosix carbon atoms such as methanol, hexanol or cyclohexanol; a phenoliccompound such as phenol or cresol; aniline; diethylamine; thiophenol andso forth. Displacing compounds having a trialkylsilyl counter-moiety canbe synthesized by known methods, such as by refluxing the compoundhaving a hydrogen counter-moiety with hexaalkyldisilazane. Displacingcompounds having an alkali metal salt ion counter-moiety can besynthesized by known methods, such as contacting the compound having ahydrogen counter-moiety with a base-containing alkali metal ions.

The process may be carried out without a solvent at temperatures abovethe melting point of the reagents. The process is preferably carried outin a polar organic solvent, such as N-methylpyrrolidone, dimethylsulfoxide, dimethyl acetamide, diphenyl sulfone and benzophenone. If thecounter-moiety will not dissociate from the nucleophilic moiety in thesolvent, then an activating compound capable of removing thecounter-moiety should be added. Appropriate solvents and activatingcompounds for aromatic nucleophilic substitution are known to persons ofordinary skill in the art. The appropriate solvent and activatingcompound depend upon the choice of reagent.

If the counter-moiety is an alkali metal cation, no activating compoundis ordinarily necessary because the salt ordinarily dissociates in anyof the preferred solvents named above without a catalyst. If thecounter-moiety is a trialkylsilyl moiety, the activating compound ispreferably a catalytic amount of alkali metal halide salt. A preferredalkali metal halide salt is cesium fluoride. If the counter-moiety is ahydrogen atom, the activating compound is preferably a stoichiometricamount of strong base such as an alkali metal hydroxide, phenate orcarbonate. Examples of preferred strong bases include sodium hydroxide,potassium carbonate and cesium phenate. If a solvent is used inconnection with a strong base, the solvent should be an aprotic solventsuch as N-methylpyrrolidone, dimethyl sulfoxide and dimethyl acetamide.Trialkylsilyl counter-moieties may also be used with basic catalysts.

The reaction preferably takes place in an anhydrous environment under aninert atmosphere. Examples of suitable inert gases include nitrogen,helium and argon. The pressure of the reaction may be subatmospheric orsuperatmospheric, but is conveniently about atmospheric pressure. Thepressure is preferably low enough that volatile by-products of thereaction, such as trimethylsilyl halide, will distill off under reactiontemperatures. An anhydrous environment may be generated by known methodssuch as adding to the solvent a small amount of cosolvent, such astoluene, chlorobenzene or xylene, which can remove water by azeotropicdistillation.

The process takes place at a temperature high enough that the reactionmay occur and low enough that the reagents do not decompose or distilloff, and the products do not decompose. Optimal temperatures varyaccording to the reagents used and may readily be determined byexperiment. Ordinarily, processes having a strong base as an activatingcompound proceed at lower temperatures than those having an alkali metalhalide. Ordinarily, processes carried out without a solvent proceed athigher temperatures than those with a solvent to keep the reagentsand/or products in liquid form. However, the temperature is preferablyat least about 140° C.; more preferably at least about 160° C.; and mostpreferably at least about 200° C. The maximum temperature is notcritical but is preferably at most about 400° C. more preferably at mostabout 350° C. and most preferably at most about 325° C.

The time for the reaction to go to completion varies as a function ofthe reagents used and the conditions under which they are reacted. Thereaction is preferably essentially completed within about 5 hours, morepreferably within about 3 hours. The yield of product is preferably atleast about 80 percent, highly preferably at least about 90 percent,more preferably at least about 95 percent and most preferably at leastabout 99 percent.

The reaction preferably conforms to the formula set out in Formula 4:##STR4## wherein: A is an organic moiety of the displacing compound, aspreviously defined;

Ar* is an aromatic group of the azole-containing compound, as previouslydefined;

Z is as previously defined in describing the azole rings.

L is a leaving group as previously described;

Nu is --O--, --S--, or --NR-- as previously described in describing thenucleophilic moiety; and

Y is a counter-moiety for the nucleophilic moiety as previouslydescribed.

Of course, the organic moiety of the displacing compound (A) may bebonded to other reactive or inert groups which do not interfere with thereaction. Likewise, the azole ring may be bonded or fused with otherreactive or inert groups which do not interfere with the reaction.

The nucleophilic displacement reactions of the present invention can beused conveniently in a process for synthesizing non-rigid-rod polymers.The non-rigid rod polymer is formed by the condensation polymerizationof at least one difunctional monomer. Each difunctional monomercontains; (1) an organic moiety which is inert with respect to allpolymerization reagents under polymerization conditions; and (g) atleast two reactive groups selected such that a reaction betweenmonomers, as previously described, may occur to form a polymer.

The organic moiety may be aromatic, aliphatic or aromatic-aliphatic.Aliphatic moieties within the organic moiety are preferably alkyl orhalogenated alkyl. Aromatic groups within the organic moiety have thedescription and preferred embodiments previously defined. Each organicmoiety is preferably independently aromatic-aliphatic or aromatic. Eachorganic moiety is most preferably an aromatic group.

Each monomer contains two reactive groups selected from azole-containinggroups and displacing groups. Azole-containing groups comprise;

(1) an azole ring, as previously defined, bonded to the organic moiety;

(2) an aromatic group, as previously defined, bonded to the 2-carbon ofthe azole ring; and

(3) a leaving group, as previously defined, bonded to the aromatic groupin a position where it is activated by the azole ring.

The previous discussions regarding the position of the leaving groupwith respect to the azole-containing group and regarding the position ofsubstituents around the leaving group applies to monomers used for thepresent invention. The azole ring is highly preferably fused to anaromatic group in the organic moiety.

Displacing groups comprise:

(1) a nucleophilic moiety, as previously described, bonded to theorganic moiety; and

(2) a counter-moiety, as previously described, bonded to thenucleophilic moiety.

The nucleophilic moiety should be bonded to the organic moiety at apoint where the organic moiety does not exert a substantialelectron-withdrawing influence upon it. The previous discussionregarding the placement of substituents which interfere with thereactions of the nucleophilic moiety applies to monomer used for thepresent invention.

Monomers used in the present invention may be AB-monomers, in which eachmonomer comprises an azole-containing group and a displacing group.AB-monomers can polymerize with each other, so that no second monomer isneeded. Preferred AB-monomers useful for the present invention arediscussed hereinafter.

Alternatively, approximate equimolar amounts of AA-monomer andBB-monomer can be polymerized. AA-monomers each comprise twoazole-containing groups, and BB-monomers each comprise two displacinggroups. Preferred AA-monomers d to the organic moiety; and

(2) Preferably, the polymerization is carried out in the presence of aslight molar excess of either AA- or BB-monomer. The excess is preferredin order to hold down the molecular weight, because excessive molecularweight of the resulting polymer makes it less thermoplastic withoutsubstantially improving its physical properties. The excess ispreferably no more than about 2 mole percent, more preferably no lessthan about 0.5 mole percent and most preferably about 1 mole percent.

Of course, obvious variations in the monomers polymerized may bepracticed to achieve obvious variations in the resulting polymers. Forinstance, a mixture of monomers containing oxazole, thiazole and/orimidazole rings can be polymerized to form random PBO, PBT and PBIcopolymers. AB-monomer can be polymerized in a mixture withapproximately equimolar amounts of AA-monomer and BB-monomer to form arandom copolymer containing both AB-polymer and AA/BB polymer mer units.Monomers containing different aromatic groups or nucleophilic moietiesmay likewise be polymerized to form random copolymers containing variedaromatic groups and linkages between mer units. Small amounts ofmonofunctional compounds, such as the displacing compounds andazole-containing compounds previously described, can be added aschain-terminating agents. A small amount of trifunctional monomer suchas 1,3,5-trihydroxybenzene can be added to cause cross-linking.

The conditions for polymerization are substantially the same as thosepreviously described for the reaction of displacing compounds andazole-containing compounds. If no solvent is used, the temperature ispreferably at least the melting point of the monomer or monomers and thepolymer. If solvent is used, the temperature may be lower. Thetemperature should be low enough that the reagents and the resultingpolymer are stable. The reaction preferably takes place in an anhydrousenvironment under an inert atmosphere.

Polymers produced by the process are described in further detail afterthe description of preferred monomers.

AB-Monomers

AB-monomers useful in the practice of the present invention preferablycomprise;

(1) a first aromatic group;

(2) an azole ring fused to said first aromatic group;

(3) a second aromatic group bonded to the 2-carbon of said azole ring;

(4) a leaving group bonded to said second aromatic group in a positionwhere it is activated by said azole ring;

(5) a nucleophilic moiety, as previously defined, linked to said firstaromatic group in a position not ortho to the 4- or 5-carbon of saidazole ring; and

(6) a counter-moiety, as previously defined, bonded to said nucleophilicmoiety.

The first aromatic group, the azole ring and the leaving group have thedescription and preferred embodiments previously defined for theirrespective groups. The second aromatic group has the definition andpreferred embodiments previously given for an aromatic group in anazole-containing compound or group. In particular, the discussionsregarding the positioning of the azole ring, the leaving group, and anysubstituents apply.

The nucleophilic moiety and the counter-moiety have the samedescriptions and preferred embodiments previously given. Thenucleophilic moiety is linked to the first aromatic group by a bond orby a divalent organic moiety. The divalent organic moiety should benon-electron-withdrawing. It preferably comprises no more than about 12carbon atoms, more preferably no more than about g carbon atoms and morehighly preferably no more than about 1 carbon atom. Most preferably, themonomer contains no divalent organic moiety, and the nucleophilic moietyis bonded directly to the first aromatic group. If the first aromaticgroup comprises an unfused ring system, then the nucleophilic moiety ispreferably bonded to the aromatic moiety which is not fused with theazole ring. The nucleophilic moiety is highly preferably an oxygen atomor a sulfur atom.

AB-monomers preferably conform with Formula 5(a); ##STR5## wherein Ar¹is a first aromatic group as previously described, Ar² is a secondaromatic group as previously described. A is a bond or a divalentorganic moiety as previously described, and all other characters havethe meanings previously assigned. AB-monomers more preferably conformwith Formula 5(b) or 5(c); ##STR6## wherein Y is a hydrogen atom, atrialkylsilyl group or an alkali metal cation; L is chlorine orfluorine; Nu is a sulfur atom or an oxygen atom; and Z is as previouslydescribed. A less preferred embodiment conforms to Formula 5(d):##STR7## wherein all characters have the meaning previously described.

The most preferred AB-monomers are5-hydroxy-2-(p-fluorophenyl)benzoxazole,6-hydroxy-2-(p-fluorophenyl)benzoxazole and the alkali metal salt andtrimethylsilyl derivatives thereof.

AB-monomers of the present invention can be synthesized by simplevariation of reagents in known reactions such as those previouslydescribed for the synthesis of azole-containing compounds. For instance,AB-monomers are formed by the reaction of a first compound having:

(1) an aromatic group corresponding to the first aromatic group of themonomer (Ar¹);

(2) an o-amino-basic moiety, as that moiety is previously described,bonded to said aromatic group, and

(3) a nucleophilic moiety linked to said aromatic group (Ar¹) and bondedto a hydrogen atom with a second compound having:

(1) an aromatic group corresponding to the second aromatic group of themonomer (Ar²);

(2) an "electron-deficient carbon group", as that term is previouslydefined, bonded to said aromatic group; and

(3) a leaving group, as that term is previously defined, bonded to saidaromatic group.

The first compounds are known and can be synthesized by known processes,such as those described in Mital et al., "Synthesis of Some5-Substituted 2-Aminobenzenethiols and their Conversion intoPhenothiazines via Smiles Rearrangement", 1969 J. Chem. Soc. (C) 2148(1969); and Henrich et al., "Ueber Derivate des 4-Amidoresorcins", 35Chem. Berichte 4195 (1902) and the references cited therein, which areincorporated herein by reference. Preferred first compounds are2-aminohydroquinone and 2-aminoresorcinol. The second compounds are alsoknown and can be synthesized by known methods, such as by halogenatingbenzoic acid. Preferred second compounds are the p-halobenzoic acids andp-halobenzoyl halides.

Preferably, the first compound is dissolved in an aprotic solvent suchas N-methylpyrrolidone under an inert atmosphere. A slight excess of thesecond compound is added to the mixture and the mixture is heated toreflux temperature for a time sufficient for all reagents to react,preferably about 2 hours. After permitting the mixture to cool, it isdiluted with excess water and potassium carbonate is added. The productprecipitates and may be filtered out of the solution. It may be purifiedby known methods such as recrystallization from ethanol and water.Procedures described in Bogert et al., "Researches on Thiazoles, XX", 57J. Am. Chem. Soc. 1529 (1935); Henrich et al., "Ueber Derivate des4-Amidoresorcins", 35 Chem. Berichte 4195 (1902) and Henrich et al.,"Beitrgge zur Kenntniss des Zusammenshangs zwischen Flourescenz undchemischer Constitution bei Derivativen des Benzoxazols", 37 Chem.Berichte 3108 (1904), which are incorporated herein can also be modifiedby substitution of reagents to provide compounds of the presentinvention.

The alkali metal salt and trialkylsilyl derivatives of those monomerscan be produced by the methods already described. However, if themonomer is contacted with a base to generate the alkali metal salt, thetemperature should be low enough to prevent substantial polymerizationof the monomer.

AA/BB-Monomer Systems

AA/BB-monomer systems comprise an AA-monomer having two azole-containingreactive groups and a BB-monomer having two nucleophilic reactivegroups. The AA-monomer preferably comprises;

(1) a first aromatic group (Ar¹);

(2) a first and a second azole ring fused to said first aromatic group;

(3) a second aromatic group (Ar²) bonded to the 2-carbon of said firstazole ring and a third aromatic group (Ar³) bonded to the 2-carbon ofsaid second aromatic group; and

(4) a first leaving group bonded to said second aromatic group and asecond leaving group bonded to said third aromatic group, each in aposition where it is activated by one of the azole rings.

The first aromatic group and the azole groups have the descriptionspreviously given. The second and third aromatic groups have thedescriptions and preferred embodiments previously given for aromaticgroups which are bonded to an azole group and to a leaving group. Theleaving groups have the description and preferred embodiments previouslygiven for leaving groups. They are highly preferably in ortho or paraposition, and most preferably in para position, with respect to theazole rings.

In AA-monomers, the first aromatic group (Ar¹) is preferably an unfusedsystem comprising two aromatic moieties (Ar^(1a) and Ar^(1b)) linked bya bond or a divalent linking moiety (D). as previously described indefining aromatic groups. The two aromatic moieties are more preferablylinked by a divalent linking moiety. The first azole ring is fused toone aromatic moiety (Ar^(1a)) and the second azole ring is fused to theother aromatic moiety (Ar^(1b)). The second and third aromatic groupsare bonded to the azole rings, and the leaving groups are bonded to thesecond and third aromatic groups, as previously described.

The AA-monomer preferably conforms to Formula 6(a): ##STR8## whereinAr¹, Ar² and Ar³ are respectively the first, second and third aromaticgroups as previously described and all other characters have themeanings previously given. The AA-monomer more preferably conforms toFormula 6b: ##STR9## wherein Ar^(1a) and Ar^(1b) are aromatic moietieswithin the first aromatic group (Ar¹) as previously defined, D is adivalent linking moiety, and all other characters have the meanings andpreferred embodiments previously given.

AA-monomers can be synthesized by simple and simple variations on knownprocesses. For instance, they may be synthesized by the reaction twoequivalents of a compound having:

(1) an aromatic group corresponding to the second and third aromaticgroups of the AA-monomer (Ar² and Ar³):

(2) an "electron-deficient carbon group" bonded to said aromatic group;and

(3) a leaving groups as previously defined:

with a compound having:

(1) an aromatic group corresponding to the first aromatic group of theAA-monomer (Ar¹): and

(2) two o-amino-basic moieties bonded to said aromatic group.

Compounds having an aromatic group bonded to two o-amino-basic moieties,and the synthesis of those compounds, are described in Wolfe, LiquidCrystalline Polymer Compositions, Process and Products, U.S. Pat. No.4,533,693 (Aug. 6, 1985) at Columns 19-24; in Lysenko, High PurityProcess for the Preparation of 4,6-Diamino-1,3-Benzenediol, U.S. Pat.No. 4,776,244: and in Inbasekaren et al., Ser. No. 864,063, filed May16, 1986, which are incorporated herein by reference. The reactionconditions are similar to those described for synthesizing theself-polymerizing monomer.

Alternatively, the AA-monomer can be synthesized in a three-stepprocess. First, an diamide is formed by reacting two equivalents abenzoic acid or acid chloride having a leaving group with an aromaticcompound having two primary amine substituents. Second, two bromineatoms are introduced ortho to the amide groups by contacting the amidewith 2.2 equivalents of molecular bromine. Third, the o-bromoamidemoiety is cyclized to form the azole ring by reaction in a solvent suchas dimethyl acetamide in the presence of a mild acid such as potassiumcarbonate under inert atmosphere catalyzed by copper powder.

Alternatively, monomers wherein Ar¹ is an unfused system having twoaromatic moieties linked by a divalent linking moiety can be synthesizedby reacting two moles of AB-monomer having hydrogen as thecounter-moiety, as previously described, with one mole of a compoundhaving two carboxylic acid groups under conditions such that the ester,amide or thioester is formed. The diacid compound becomes the divalentlinking moiety (D) as that term is previously described. SimplerAA-monomers can be synthesized by the process described in 94 Chem.Abstracts 174948w, which is incorporated herein by reference.

BB-monomers preferably comprise:

(1) an organic moiety (A) which is not electron-withdrawing and which isinert with respect to all reagents under reaction conditions;

(2) two nucleophilic moieties, as that term is previously described,bonded to said divalent organic moiety: and

(3) two counter-moieties, as that term is previously described, bondedto the nucleophilic ions.

The organic moiety (A) has the same description and preferredembodiments previously given to describe the organic moiety in amonomer. It preferably comprises an aromatic group (Ar⁴) having thedescription and preferred embodiments previously given for aromaticgroups. All other moieties have the descriptions and preferredembodiments previously given. If the organic moiety (A) comprises anaromatic group (Ar⁴), the nucleophilic moieties are preferably linked tothe aromatic group in meta or para position with respect to each other,and more preferably in para position.

Alternatively, a bis-(alkali metal) sulfide may serve as a BB-monomer.

Suitable BB-monomers are commercially available and others can readilybe synthesized by known methods. Examples of preferred BB-monomersinclude hydroquinone, resorcinol, hydroxybenzyl alcohol, sulfonylbisphenol, bisphenol A, aminophenol, phenylenediamine, sulfonyldianiline, benzidine, 2-mercaptoethanol, 4-mercaptophenol,4-hydroxy-2-thiopyrimidine, 4,4'-oxy-bis(phenol), 4,4'-thio-bis(phenol)and alkali metal salt and trimethylsilyl derivatives thereof. Disodiumsulfide is also an example of a BB-monomer. The monomers having hydrogenas a counter-moiety can be converted to monomers having othercounter-moieties by known methods previously described.

BB-monomers preferably conform to Formula 7:

    7(a) Y--Nu--A--Nu--Y,,

and more preferably conform to Formula 7(b):

    7(b) Y--Nu--Ar.sup.4 --Nu--Y

wherein A is a divalent organic moiety as previously described: Ar⁴ isan aromatic group and all other characters have the meanings previouslyassigned.

Polymers Synthesized by Processes and Monomers of the Invention

The polymers synthesized according to the process of the presentinvention contain a plurality of mer units which fall into one of twospecies. AB-polymers contain mer units comprising:

(1) a first aromatic group:

(2) an azole ring fused to said first aromatic group:

(3) a second aromatic group bonded to the 2-carbon of said azole ring:and

(4) an oxygen, sulfur or nitrogen atom linked to said first aromaticgroup and bonded by a single bond to the second aromatic group of anadjacent mer unit.

The first and second aromatic groups and the oxygen, sulfur or nitrogenatom in the polymer correspond to, and have the definition and preferredembodiments of, the first and second aromatic groups and thenucleophilic moiety of the AB-monomer. The oxygen, sulfur or nitrogenatom may be linked to the first aromatic group by a divalent organicmoiety (A) having the description previously given in describingAB-monomers, or it may be bonded directly to the first aromatic group.It is preferably bonded directly to the first aromatic group.

The polymer synthesized by the reaction of an AB-monomer preferablycontains a plurality of units which conform with Formula 8: ##STR10##wherein all characters have the meanings previously assigned indescribing AB-monomers. The polymer more preferably contains a pluralityof units which conform with either Formula 9(a) or 9(b): ##STR11##wherein Z and Nu are each independently either an oxygen atom or asulfur atom. The polymer most preferably contains a plurality of unitswhich conform with either Formula 9(a) or 9(b) wherein Z and Nu are eachan oxygen atom.

AA/BB-polymers preferably contain a plurality of repeating units whichcomprise:

(1) a first aromatic group (Ar¹);

(2) a first and a second azole ring fused to said first aromatic group;

(3) a second aromatic group (Ar²) bonded to the 2-carbon of said firstazole ring and a third aromatic group (Ar³) bonded to the 2-carbon ofsaid second aromatic group;

(4) a first oxygen, sulfur or nitrogen atom bonded to said secondaromatic group and a second oxygen, sulfur or nitrogen atom bonded tosaid first aromatic group; and

(5) an organic moiety (A) bonded to said second oxygen, sulfur ornitrogen atom and to the first oxygen, sulfur or nitrogen atom of anadjacent unit.

The first, second and third aromatic groups and the first and secondazole rings have the preferred embodiments previously set out for thecorresponding structures in describing the AA-monomer used in thepolymerization. The first and second oxygen, sulfur or nitrogen atomshave the description and preferred embodiments previously used todescribe nucleophilic moieties in BB-monomers. The organic moiety hasthe description and preferred embodiments of organic moieties inBB-monomers. The first and second oxygen, sulfur or nitrogen atoms arepreferably bonded to the second and third aromatic groups in thepositions previously described for leaving groups to be bonded to thosearomatic groups in the AA-monomers.

Mer units in AA/BB-polymers preferably conform with Formula 10(a):##STR12## and more preferably conform with Formula 10(b): ##STR13##wherein all characters have the meanings and preferred embodimentspreviously assigned. Mer units in AA/BB-polymers more highly preferablyconform to either Formula 11(a) or 11(b): ##STR14## wherein each Z andeach Nu is independently an oxygen atom or a sulfur atom and D is a bondor a divalent linking group as previously defined. Mer units mostpreferably comply with Formula 11(b). Each Z is most preferably anoxygen atom.

The number average molecular weight of polymer synthesized by thepresent invention is preferably at least about 5000 and more preferablyat least about 10,000. Such molecular weights are ordinarily measuredindirectly by measuring intrinsic viscosity in a solvent such asmethanesulfonic acid or concentrated sulfuric acid. The relationshipbetween intrinsic viscosity and molecular weight is different for eachindividual polymer and may vary widely from one polymer to the next.

Polymers synthesized according to the present invention are ordinarilythermoplastic. One exception is the AA/BB-polymer in which Ar¹ is a1,2,4,5-phenylene group or structurally equivalent heterocyclic moietyand Ar², Ar³ and Ar⁴ are p-phenylene groups or structurally equivalentbiphenylene or heterocyclic moieties. Those polymers ordinarily have noglass transition temperature below their decomposition temperature.Glass transition temperatures of thermoplastic polymers vary accordingto the polymer structure, composition and molecular weight. Likewise,preferred glass transition temperatures will vary according to thepolymer and its intended use.

It has surprisingly been discovered that PBZ polymers synthesizedaccording to the process of the present invention experience slower lossof weight due to thermal oxidation at high temperatures than do similarPBZ polymers synthesized in polyphosphoric acid according to the priorart processes. It is theorized, without intending to be bound thereby,that the prior art polymers retain some phosphoric or polyphosphoricacid after synthesis and that the acid hastens thermal degradation ofthe polymer in air. Polymers of the present invention are notpolymerized in acid and do not contain any strong acid unless extrudedfrom acid after polymerization.

Polymers synthesized according to the process of the present inventioncan be shaped by known processes to form useful articles. For instance,the polymers may be molded at temperatures above their glass transitiontemperature. Alternatively, the polymers can be dissolved in mineralacid to form polymer dopes, which can be extruded to form useful fibers,films and shaped articles according to processes readily familiar topersons skilled in the art. See, e.g., U.S. Pat. No. 4,533,693 atColumns 82-84; Chenevey et al., Process for Preparing Shaped Articles ofRigid Rod Heterocyclic Liquid Crystalline Polymers, U.S. Pat. No.4,606,875 (Aug. 19, 1986); Chenevey et al., Process for Preparing Filmof Poly{[Benzo(1,2-D: 4,5-D')bisthiazole-2,6-diyl]-1,4-phenylene}, itsCis Isomer or Mixtures Thereof, U.S. Pat. No. 4,487,735 (Dec. 11, 1984);Tan, Process for Producing High-Strength, Ultralow DenierPolybenzimidazole (PBI) Filaments, U.S. Pat. No. 4,263,245 (Apr. 21,1981); Hwang et al., "Solution Processing and Properties of MolecularComposite Fibers and Films", 23 Poly. Eng. & Sci. 784, 785 (1984); andHwang et al., "Composites on a Molecular Level; Phase Relationships,Processing, and Properties" , B22(2) J. Macromol. Sci.-Phys. 231, 234-35(1983), which are incorporated by reference.

Polymers synthesized according to the process of the present inventioncan be incorporated into molecular composites with rigid rod PBZpolymers. A well-mixed dope is formed comprising mineral acid, polymerssynthesized according to the present invention, and rigid rod PBZpolymer. The dope is extruded as described above. The molecularcomposites ordinarily are not substantially phase separated uponextrusion, and therefore have high tensile strength and modulus. Thecomposites do experience some phase separation upon heating to theirglass transition temperature.

Illustrative Examples

The following examples are for illustrative purposes only and should notbe interpreted as limiting the scope of either the specification or theclaims. Unless it is otherwise specified, all parts and percentages areby weight.

I. Present Invention Practiced Without Polymerization EXAMPLE 1Synthesis of 4,5-Diphenyl-2-(p-phenoxyphenyl)-1,3-oxazole

A mixture containing one gram (3.2 mmoles) of4,5-diphenyl-2-(p-fluorophenyl)-1,3-oxazole, 1.2 g (12 mmoles) ofphenol, 2 g (14.5 mmoles) of anhydrous potassium carbonate and 10 ml ofN-methylpyrrolidone (hereinafter NMP) is stirred and refluxed undernitrogen atmosphere for 40 minutes when gas chromatograph analysisindicates the disappearance of the starting material and the formationof a new compound. The reaction mixture is cooled, diluted with 30 ml ofwater, and stirred for 30 minutes. The colorless precipitate is filteredand recrystallized from 95 percent ethanol. The title compound (1.22 g,99 percent yield) is recovered. The product has a melting point of 125°C.-126° C.

EXAMPLE 2 Synthesis of 2-(o,p-Di-phenoxyphenyl)benzoxazole

The procedure of Example 1 is repeated using 1.5 g (5.7 mmoles) of2-(o,p-dichlorophenyl)benzoxazole, 4 g (42 mmoles) of phenol, 3 g (21.7mmoles) of potassium carbonate and 13 ml of NMP with reflux for 2.5hours. The title product (1.95 g, 92.1 percent yield) is recovered.

EXAMPLE 3 Synthesis of2-(2',4'-bis(p-methoxyphenyl)thiophenoxy)]benzoxazole

A mixture of 2.64 g (10 mmoles) of 2-(2',4'-dichlorophenyl)benzoxazole,4.0 g (30 mmoles) of potassium carbonate, 3.36 g (24 mmoles) of4-methoxybenzenethiol and 20 ml of NMP is stirred and refluxed undernitrogen atmosphere for one hour. The mixture is cooled, diluted with 50ml of water and extracted with two 40-ml portions of methylene chloride.The methylene chloride extracts are dried with magnesium sulfate andevaporated to provide a colorless solid. The title product isrecrystallized from the colorless solid using aqueous ethanol. The yieldis 3.9 g (82.5 percent) of colorless needles having a melting point of151° C.-155° C.

EXAMPLE 4 Synthesis of 2-(p-phenoxyphenyl)benzoxazole

A mixture of 1.20 g (5 mmoles) of 2-(p-nitrophenyl)benzoxazole, 0.80 g(8.5 mmoles) of phenol, 2 g of potassium carbonate and 15 ml of NMP isstirred and refluxed under nitrogen atmosphere for one hour. The titleproduct is recovered from the resulting solution as described inExample 1. The recovery is 1.15 g (80.4 percent yield). The product hasa melting point of 70° C.-71° C. The experiment is repeated using2-4(p-fluorophenyl)benzoxazole as the reagent and the title product isobtained in 90 percent yield.

EXAMPLE 5 Synthesis of 2-(p-methoxyphenyl)benzoxazole

A mixture of 1.15 g (5 mmoles) of 2-(p-chlorophenyl)benzoxazole, 2.5 gof sodium methoxide and 10 ml of dimethyl sulfoxide is heated at 80°C.-90° C. under nitrogen atmosphere for one hour. The mixture is cooledand diluted with 100 ml of water. The title compound (1 g, 87 percentyield) precipitates and is recovered. It has a melting point of 99.5°C.-101.5° C.

EXAMPLE 6 Synthesis of 5-chloro-2-(4-piperidinophenyl)benzoxazole

A mixture containing 2.48 g (10 mmoles) of5-chloro-2-(4-fluorophenyl)benzoxazole, 2.55 g (30 mmoles) of piperidineand 15 ml of NMP is heated with stirring under nitrogen atmosphere at100° C. for 16 hours. The reaction is complete as judged by GC analysis.The mixture is cooled, poured into 100 ml of water and stirred for 30minutes. The title compound (3.05 g, 97 percent yield) is filtered andwashed. It has a melting point of 162° C.-164° C.

II. Synthesis and Polymerization of AB-Monomers EXAMPLE 7 Synthesis of2-(4-Fluorophenyl)-6-hydroxybenzoxazole

4-Aminoresorcinol HCl salt (1.61 g) is dissolved in 10 ml of NMP undernitrogen atmosphere. 4-Fluorobenzoyl chloride (1.91 g) is added all atonce and the mixture is heated under reflux for approximately 2 hours.After reflux, the mixture is allowed to cool and is diluted with 60 mlof water. Potassium carbonate (3.5 g) is added and the mixture isstirred. The resulting precipitate is filtered and recrystallized fromethanol and water to yield 1.85 g of the above-named product. Theproduct melts at 225° C.-227° C.

EXAMPLE 8 Synthesis of 2-(4-Fluorophenyl)-5-hydroxybenzoxazole

The procedure of Example 7 is repeated using 1.61 g of2-aminohydroquinone HCl salt in place of the 4-aminoresorcinol salt. Theabove-named product is obtained and has a melting point of about 166°C.-168° C.

EXAMPLE 9 Synthesis of 2-(4-Fluorophenyl)-6-hydroxybenzothiazole

The procedure set out in Example 7 is repeated using2-amino-5-methoxybenzenethiol and 4-fluorobenzoyl chloride. The reactionyields a mixture of the title compound and2-(4-fluorophenyl)-6-methoxybenzothiazole. The mixture is treated withexcess boiling 48 percent HBr for one hour to convert the latter productto the title compound. The solution is filtered and the precipitate isrecrystallized from ethanol and water. The overall yield is 80.3 percentbased on the initial amount of benzenethiol. A recrystallized productmelts at about 221° C.-223° C.

EXAMPLE 10 Synthesis of2-(4-Fluorophenyl)-5,7-diaza-6-hydroxy-benzoxazole

The procedure set out in Example 7 is repeated using5-amino-2,4-dihydroxypyrimidine and 4-fluorobenzoyl chloride. The titlecompound is obtained as an off-white amorphous solid with a meltingpoint of about 355° C.-357° C.

EXAMPLE 11 Synthesis of Trimethylsilyl Monomers

(a) 2-(4-Fluorophenyl)-6-hydroxybenzoxazole (20.43 g, 89.13 mmoles) fromExample 7 is mixed with 90 ml of hexamethyldisilazane. The mixture isrefluxed for 260 minutes and then the excess silating agent is distilledoff at 80° C. and 20 mm Hg. The product is purified by bulb-to-bulbdistillation. 2-(4-Fluorophenyl)-6-(trimethylsilylether)benzoxazole(25.49 g, 95 percent yield) is recovered, having a melting point of 2095.5° C.-96.5° C.

(b) The procedure of Example 11(a) is repeated using 10.57 g of themonomer from Example 8 and 50 ml of hexamethyldisilazane, and reactingfor 7 hours. The product2-(4-fluorophenyl)-5-(trimethylsilylether)benzoxazole has a meltingpoint of 222° C.-224° C.

(c) The procedure of Example 11(a) is repeated using 10.59 g of theproduct of Example 9 and 50 ml of hexamethyldisilazane and refluxing forabout 15 hours. The product2-(4-fluorophenyl)-5-(trimethylsilylether)benzothiazole has a meltingpoint of 79.5° C.-80° C.

EXAMPLE 12 Polymer from Monomer of Example 11(a)

A resin kettle equipped with a short path still and a nitrogen inlet ischarged with 10 g of diphenylsulfone, 10 g of the compound prepared inExample 11(a) and 25 ml of chlorobenzene. The mixture is stirred as thechlorobenzene is distilled off slowly to azeotropically remove water.Cesium fluoride (21.8 mg) is added and the mixture is heated from 280°C. to 350° C. over a 30-minute period. After an additional 70 minutes,the flask is removed from the heat and allowed to cool. The resultingpolymer is recovered and placed in a Soxhlet extractor with refluxingmethylene chloride overnight. It is then placed in a vacuum oven at 150°C. overnight. The resulting polymer has an inherent viscosity of 1.99dL/g in concentrated sulfuric acid (0.5 g/dL at 25° C.) and an inherentviscosity of 7.18 dL/g in methanesulfonic acid (0.2 g/dL at 25° C.). DSCscan reveals a broad Tm at 370° C. A rescan reveals a Tg at 198° C.Analysis by TGA at 50 ml/min. airflow rate and 10° C./min. heating showsthat the polymer has a 1 percent weight loss at 514° C. and a 5 percentweight loss at 556° C.

EXAMPLE 13 Preparation of Polymer from2-(4-Fluorophenyl)-5-trimethylsiloxy Benzoxazole

A resin kettle is charged with 10 g of diphenylsulfone and 10 g of themonomer from Example 11(b). The mixture is warmed under vacuum at 100°C. for 30 minutes to remove water. Cesium fluoride (10 mg) is added andthe kettle is evacuated and refilled with argon three times. The kettleis immersed in a molten salt bath at 250° C. After 5 minutes,trimethylsilyl fluoride begins to distill. The temperature is graduallyraised to 330° C. over 30 minutes. After 70 minutes total, thepolymerization is stopped and the polymer is purified as described inExample 12. The product has an inherent viscosity of 0.74 dL/g inconcentrated sulfuric acid and 3.91 dL/g in methanesulfonic acid. Aninitial DSC scan reveals a weak Tg at 257° C. and a strong sharp Tm at396° C. On rescan, a weak Tg at 227° C. is observed.

EXAMPLE 14 Preparation of Polymer of2-(4-Fluorophenyl)-5-trimethylsiloxy Benzothiazole

A resin kettle equipped with a short path still and a nitrogen inlet ischarged with 12 g of diphenylsulfone and 25 ml of chlorobenzene. Thechlorobenzene is distilled off slowly with stirring to azeotropicallyremove water. The monomer from Example 11(c) (11.4 g) is washed with 5ml of chlorobenzene and 48.9 mg of cesium fluoride is introduced. Thesolution is heated from 280° C. to 300° C. Trimethylsilylfluoride isimmediately generated. After 11 minutes, the temperature is raised to330° C. and reaction is continued for 84 minutes. The polymer isisolated as described in Example 12. It has an inherent viscosity of0.55 dL/g in concentrated sulfuric acid. An initial DSC scan reveals astrong sharp Tm at 426° C. A Tg of 247° C. is observed on rescan.

III. Synthesis of AA-Monomers and Polymerization with BB-MonomersEXAMPLE 15 Synthesis of 2,6-Di(p-fluorophenyl)benzobisoxazole (cismonomer)

N,N'-Bis(p-fluorobenzoyl)-1,3-diaminobenzene is contacted with 2.2equivalents of bromine in acetic acid at 70° C. for one hour to yield1,3-dibromo-4,6-bis-(p-fluorobenzamido)benzene. That product (30.6 g,0.06 mole) is stirred with 200 ml of dimethyl acetamide under nitrogenatmosphere. Copper powder (3 g) and 16.5 g of potassium carbonate isadded and the mixture is refluxed for one hour. After cooling to ambienttemperature, the precipitated product is filtered and washed with dilutenitric acid, with water and with ethanol. The title compound (16.9 g,80.9 percent yield) shown in Formula 12 is recovered. Its meltingtemperature, as shown by DSC is 361.4° C. ##STR15##

EXAMPLE 16 Synthesis of2,6-Di(p-fluorophenyl)benzo[1,2-d;4,5-d']-bisoxazole (trans monomer)

The dihydrogen chloride salt of 2,5-diamino-1,4-hydroquinone (3.2 g,0.015 mole) is added with stirring to 30 ml of NMP under nitrogenatmosphere. p-Fluorobenzoyl chloride (5.8 g, 0.036 mole) is added over30 minutes at 170° C. The mixture is refluxed for 3 hours and thencooled. The resulting precipitate is filtered and washed with water,ethanol and ether. The product, shown in Formula 13, is thenrecrystallized from dimethyl sulfoxide to provide 4.70 g (92.1 percentyield) of the title compound having a melting point in excess of 340° C.##STR16##

EXAMPLE 17 Synthesis of Bis-(6-(2-(p-fluorophenyl))benzoxazole)

The dihydrogen iodide salt of 3,3'-dihydroxy-4,4'-diaminobiphenyl (2.93g, 0.062 mole) is mixed with 100 ml of NMP under nitrogen atmosphere.p-Fluorobenzoyl chloride (19.66 g, 0.124 mole) is added dropwise and themixture is slowly heated to reflux over a period of about one hour.After 2 hours reflux the mixture is cooled. Water (600 ml) is added andstirred for 30 minutes. The resulting precipitate is filtered, washedwith water and ethanol and dried. The title compound, shown in Formula14 (21 g, 80.8 percent yield) is obtained having a melting point of 273°C.-275° C. ##STR17##

EXAMPLE 18 - Synthesis of1,3-Bis-[2-(p-fluorophenyl)-6-benzoxazolyl]benzene

Benzoxazolone (59.4 g, 0.44 mole), isophthalic acid (33.2 g, 0.20 mole)and 550 g of polyphosphoric acid are heated under nitrogen atmosphere to140° C. over 30 minutes with stirring. The mixture is heated to 170° C.over 45 minutes and is stirred at 170° C. for one hour. The mixture iscooled to 130° C. and poured carefully into 3 liters of ice water. Themixture is stirred for 15 minutes and the precipitate is filtered. Theprecipitate is washed with water, 10 percent sodium hydrocarbonatesolution, more water and then ethanol. Crude bis-keto-bisbenzoxazolone(80 g, 100 percent yield) is recovered. A small amount is recrystallizedfrom DMF and melts at 357° C.-359° C.

The crude bis-keto-bisbenzoxazolone product from the previous paragraphis stirred and refluxed with 1.5 liters of 5N sodium hydroxide solutionunder nitrogen atmosphere for 16 hours. The resulting mixture is cooled,diluted with 500 ml of water and neutralized with 580 ml of concentratedhydrochloric acid. After settling for a few hours, the resultingprecipitate is filtered, washed with water and recrystallized from a 9:1mixture of water and ethanol by volume.1,3-Bis-(4-amino-3-hydroxybenzoyl)benzene (51 g, 73.3 percent yield) isrecovered.

The recrystallized product from the preceding paragraph is mixed with200 ml of NMP under nitrogen atmosphere. p-Fluorobenzoyl chloride (38.0g, 0.24 mole) is added dropwise. The mixture is heated at 120° C.-140°C. for one hour and at reflux for 2 hours. The mixture is cooled to 70°C. and 500 ml of ethanol is added with stirring. After 15 minutes theresulting precipitate is filtered and recrystallized from NMP. The titlecompound (50.6 g, 90 percent yield) illustrated in Formula 15 isrecovered and has a melting point of 87.5° C.-289° C. ##STR18##

EXAMPLE 1 Synthesis of1,3-Bis-(2-(p-fluorophenyl)benzoxazole-6-oxycarbonyl)propane

6-Hydroxy-2-(p-fluorophenyl)benzoxazole (20.00 g, 0.087 mole) fromExample 7 is mixed with 300 ml of toluene and 12 g (0.12 mole) oftriethylamine under nitrogen atmosphere. Glutaryl chloride (7.10 g,0.042 mole) is added and the mixture is stirred and heated at reflux for5 hours. After cooling to room temperature 300 ml of 1N hydrogenchloride is added and stirring is continued for a few minutes. Theresulting precipitate is filtered and recrystallized from DMF. The titlecompound (20.5 g, 88 percent yield), illustrated in Formula 16, isrecovered and has a melting point of 189° C.-190° C. ##STR19##

EXAMPLE 20 of Poly(cis-benzobisoxazole(diphenoxybenzene))Polymer

The monomer from Example 15 (5.008 g, 14.378 mmoles) is mixed with 11 gof diphenylsulfone, 25 ml of chlorobenzene, and 3.659 g (14.378 mmoles)of bis-(trimethylsiloxy)benzene under nitrogen atmosphere. The mixtureis heated to distill the chlorobenzene to dehydrate the monomers andsolvent. Cesium fluoride catalyst (19.4 mg) is added and the mixture isheated to 280° C. After 80 minutes the mixture is heated to 330° C. for5hours. The resulting precipitate is placed in a Soxhlet extractorovernight with methylene chloride and then dried overnight at 150° C. ina vacuum oven. The title polymer, illustrated in Formula 17, isrecovered. It has an inherent viscosity of 0.35 dL/g in concentratedsulfuric acid and an inherent viscosity of 0.84 dL/g in methanesulfonicacid at 25° C. The polymer has no observable glass transitiontemperature below 450° C. ##STR20##

The polymer is analyzed by TGA at 316° C. under air flowing at 50ml/minute. After 20 hours, the polymer retains 95 percent of its initialweight and after 90 hours, the polymer retains about 85 percent of itsinitial weight.

EXAMPLE 21 Synthesis of Thermoplastic PBO Polymer

The monomer prepared in Example 18 (8.000 g, 14.37 mmoles) is mixedunder nitrogen with 15.00 g of diphenylsulfone and 25 ml ofchlorobenzene. The chlorobenzene is distilled off at atmosphericpressure to dehydrate the starting materials.Bis-(p-trimethylsiloxyphenyl)ether (4.932 g, 14.23 mmoles) and 57.9 mgof cesium fluoride catalyst are added and washed in with 4 ml ofchlorobenzene. The mixture is heated with stirring to 275° C. After 15minutes, the temperature is raised to 286° C. The resulting polymercrystallizes making stirring difficult. The polymer is placed in aSoxhlet extractor with methylene chloride overnight and dried in avacuum oven at 140° C. overnight. The resulting polymer, illustrated inFormula 18, has an inherent viscosity in concentrated sulfuric acid of1.01 dL/g. After annealing for 24 hours at 250° C., it has a glasstransition temperature of 196° C. and a melting point of 290° C.##STR21##

Samples of the polymer are compression molded into films having0.02-inch thickness. Tensile data is acquired from molded mircotensilebars of polymer according to ASTM D-1708. The polymer has a tensilemodulus of 532 kpsi, a yield stress of 14.6 kpsi, a yield strain of 13.0kpsi and an ultimate elongation of 15 percent.

EXAMPLE 22 Synthesis of Thermoplastic PBO Polymer

The procedure of Example 21 is repeated using 5.517 g (9.913 mmoles) ofthe monomer from Example 18, 12.88 g of diphenylsulfone, 25 ml ofchlorobenzene, 3.436 g (9.913 mmoles) of the bis-trimethylsiloxymonomer, 90.8 mg of cesium fluoride, and an additional 4 ml ofchlorobenzene. From 275° C., the temperature of the reaction is raisedto 320° C. over a 20-minute period until the resin becomes too viscousto stir. The product is refluxed overnight with methylene chloride,chopped into small pieces and placed in a Soxhlet extractor withadditional methylene chloride. It is then dried in a vacuum oven at 140°C. overnight. The resulting polymer, as illustrated in Example 21, hasan inherent viscosity of 3.58 dL/g in concentrated sulfuric acid. Uponan initial DSC scan a glass transition temperature of 214° C. and amelting temperature of 276° C. are observed. Upon rescan only a glasstransition temperature of 200° C. is observed.

EXAMPLE 2 Synthesis of Thermoplastic PBO Polymer

The procedure of Example 21 is followed except that 5.640 g (10.14mmoles) of the monomer from Example 18 is used with 9.074 g ofdiphenylsulfone, 25 ml of chlorobenzene, 2.579 g (10.14 mmoles) ofbistrimethylsiloxy benzene and 110.1 mg of cesium fluoride After 15minutes at 250° C., the temperature is raised to 280° C. After an hour,the reaction product is an unstirrable solid. Cesium fluoride (70.7 mg)is added and the temperature is raised to 300° C. at which point theproduct is a brown viscous oil. After one hour, the reaction mixture iscooled. The product is stirred overnight with methylene chloride andfiltered. The product is then boiled with 100 ml of 2-propanol,filtered, dried and placed in a vacuum oven at 140° C. overnight. Theresulting polymer, illustrated in Formula 19, has an inherent viscosityof 0.41 dL/g. A first DSC scan reveals two sharp endotherms at 289° C.and 318° C., while a second scan indicates only glass transitiontemperature at 177° C. ##STR22##

EXAMPLE 24 Polymer Containing Bisphenol A

The difluoride monomer from Example 18 (13.908 g, 25.0 mmoles) is mixedwith 5.650 g (24.75 mmoles) of bisphenol A, 7.60 g (55.00 mmoles) ofpotassium carbonate, 200 ml of dimethyl acetamide and 120 ml of toluene.The mixture is refluxed for 4 hours and toluene is trapped in aDean-Stark trap. Toluene is drained from the trap and the reflux iscontinued overnight. A mixture of 1:1 acetic acid and dimethyl acetamideby volume (4 ml) is added and the polymer is isolated by precipitationinto 500 ml of water in a blender while hot. The polymer is filtered,reblended once with 500 ml of cold water and reblended once with 500 mlof isopropanol. The polymer is air dried overnight and placed in avacuum oven at 140° C.-150° C. overnight. The product polymer,illustrated in Formula 20, has an inherent viscosity of 0.73 dL/g inconcentrated sulfuric acid and a glass transition temperature of 203° C.##STR23##

EXAMPLE 25 Synthesis of Polymer Containing Aliphatic Moieties

The procedure of Example 23 is followed using 13.863 g of the monomerprepared in Example 19, 5.650 g (24.75 mmoles) of bisphenol A, 7.60 g(55.00 mmoles) of potassium carbonate, 200 ml of dimethyl acetamide and120 ml of toluene. The resulting polymer is insoluble in methylenechloride, 1,1,2,2-tetrachloroethane, and dimethyl acetamide. Itdissolves with decomposition in concentrated sulfuric acid. An initialDSC scan shows a glass transition temperature of 157° C. and a meltingtemperature of 280° C., while a second scan shows only a glasstransition temperature of 157° C. The polymer has a formula shown inFormula 21. ##STR24##

What is claimed is;
 1. A process for synthesizing a di-aromatic ether,thioether or amine wherein one aromatic group is bonded to an azolering, said process comprising the step of contacting; (1) anazole-containing compound having;(a) an azole ring; (b) an aromaticgroup bonded to the 2-carbon of said azole ring; and (c) a leaving groupbonded to said aromatic group in a position such that it is activated bysaid azole ring,and (2) a displacing compound having;(a) an organicmoiety which is not electron-withdrawing and which is inert with respectto all reagents under reaction conditions; (b) a nucleophilic moietylinked to said organic moiety which nucleophilic moiety is a nitrogenatom having a hydrogen atom or an inert organic substituent, or anoxygen atom, or a sulfur atom; and (c) a counter-moiety bonded to saidnucleophilic moiety which can easily be removed therefrom,underconditions such that the counter-moiety is removed from the nucleophilicmoiety and an ether, thioether or amine linkage is formed between thearomatic group of the azole-containing compound and the organic moietyof the displacing compound.
 2. The process of claim 1 wherein thearomatic group of the azole-containing compound comprises no more thanabout 10 carbon atoms and the leaving group of the azole-containingcompound is bonded to the aromatic group in ortho or para position withrespect to the azole ring.
 3. The process of claim 2 wherein the azolering is an oxazole or thiazole ring and the leaving group is a halogenatom or an aryloxy group.
 4. The process of claim 3 wherein thenucleophilic moiety is an oxygen atom or a sulfur atom.
 5. The processof claim 4 wherein the aromatic group of the azole-containing compoundis a single six-membered ring.
 6. The process of claim 5 wherein thecounter-moiety of the nucleophilic moiety is an alkali metal ion.
 7. Theprocess of claim 6 wherein the process is carried out in a solventcapable of dissociating the alkali-metal ion from the nucleophilicmoiety.
 8. The process of claim 5 wherein the process takes place in thepresence of an activating compound suitable for nucleophilic aromaticdisplacement reactions.
 9. The process of claim 5 wherein counter-moietyof the displacing compound is a trialkylsilyl moiety.
 10. The process ofclaim 9 wherein the reaction takes place in the presence of a catalyticamount of alkali metal halide salt.
 11. The process of claim 10 whereinthe process takes place in a polar organic solvent.
 12. The process ofclaim 11 wherein the temperature of the process is between about 140° C.and about 400° C.
 13. The process of claim 12 wherein the product ether,thioether or amine is produced in yields of at least about 80 percent.14. The process of claim 5 wherein the process takes place in thepresence of a stoichiometric amount of strong base.
 15. The process ofclaim 14 wherein the reaction takes place in a polar, aprotic solvent.16. The process of claim 14 wherein the activating compound is an alkalimetal hydroxide, carbonate or phenate.
 17. The process of claim 16wherein the counter-moiety of the displacing compound is a hydrogen atomor a trimethylsilyl moiety.
 18. The process of claim 17 wherein thetemperature of the process is between about 140° C. and about 400° C.19. The process of claim 18 wherein the product ether, thioether oramine is produced in yields of at least about 80 percent.
 20. Theprocess of claim 5 wherein the leaving group is a chlorine or fluorineatom.
 21. The process of claim 20 wherein the leaving group is afluorine atom.